Thalassinidean shrimp construct species-specific burrows which vary in morphology from simple 'U' or 'Y' shaped tubes to more complex tiers of galleries or reticulate branches. Data on the burrow architecture of 44 species in 10 genera indicates that the morphological patterns of thalassinidean burrows are more diverse than previously recognized. Based on a review of these data and the existing information on thalassinidean feeding, we propose several generalizations in the form of a heuristic model relating burrow architecture and trophic mode in these fossorial decapods. Despite moderate levels of morphological variation between species, thalassinidean burrows can be categorized into 6 major groups based on their morphological characteristics The 6 burrow types are distinguishable based on the presence or absence of (1) surface sediment mounds at excurrent openings, (2) seagrasses in chambers or the burrow lining, and (3) a simple 'U' shaped burrow design. Although relatively little is known about the functional significance of the different architectural patterns, each burrow type may be indicative of one of the 3 general trophic modes utilized by burrowing shrimp: (1) deposit feeding, (2) drift catching, and (3) filter/suspension feeding. Two different types of burrows are discernible within the mound-producing, deposit-feeding group, 3 distinct burrow morphotypes are associated with filter/suspension feeding, and the 6th burrow morphotype is produced by the drift catchers. The ecological significance of these 6 burrow types is discussed in addition to the effects of various environmental parameters on mtraspecific variation in burrow morphology.

Measurements of attachment strength of the mussels Mytilus californianus and Mytilus edulis were related to measurements of drag on mussels with algal epizoans in order to understand the ecological mechanics of mussel dislodgement. Attachment strength increased with shell area, and was influenced by the location of the mussel within the aggregation, and by the exposure of the habitat. M. caljfornianus had a stronger attachment than M. edulis. In both species, significantly greater force was required to dislodge mussels at the edge of the mussel bed than at the center. The mean attachment strength of M. edulis was 15 times greater in exposed habitats than in protected habitats. In the lab and field, mussels overgrown by kelp encountered flow-induced forces that were 2 to 6 times greater than flow forces on the mussels alone. Flow-induced forces ranged from 0.12 to 1.08 Newtons, and increased with velocity from 12 to 62 cm S-'. There was no significant relation between surface area of attached kelp and drag. Flow force data and surveys of dislodged mussels at an exposed beach indicate that epizoans increase the risk of mussel dislodgement, which has ~mportant implications for intertidal mussel beds impacted by disturbance events.

Cyphoma gibbosum (Gastropoda, Ovulidae), a generalized predator on tropical gorgonians, forages selectively among gorgonian species on shallow reefs at St. Croix, U.S. Virgin Islands. Mean residence times of marked snails on prey taxa ranged from 1.8 d on Eunicea spp. to 4.7 and 10 d on Gorgonia ventalina and Plexaurella dichotoma respectively. Juveniles were sedentary and remained on single hosts throughout the study period. An analysis of wounds caused by C. gibbosum on gorgonians revealed that colonies of some taxa were consistently stripped of tissue, baring the underlying proteinaceous axis, while others were only superficially grazed. Wounds baring the axial skeleton were considerably more severe than superficial wounds because the bared skeleton could be colonized by algae causing subsequent tissue regeneration to be inhibited. Within all species, wounds were not restricted to any single portion of the colony. However, most wounds occurred within the central regions of colonies and the lowest portions of colonies were seldom damaged. The short residence times and superficial grazing on some taxa such as Eunicea spp. and Muncea spp. may be a consequence of heavy spicular armor over polyps and over the proteinaceous axis in those taxa. Deep wounds to the axial skeleton occurred only on taxa with smaller spicules and a smaller proportion of spicules in the coenenchyme by dry weight. Residence time on a prey species was inversely proportional to both maxlmum spicule length and percent composition of spicules. Short residence times and shallow wounds on colonies of h e a d y splculed species may be a response by C. gibbosum to foraging on suboptimal, heavlly defended resources Despite the short residence times, these potentially suboptimal prey taxa were regularly visited and preyed upon. This suggests that factors other than spicular architecture, such as gorgonian chemistry, may also play a role in the foraging of C. gibbosum.

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A new callianassid shrimp, Glypturus motupore, is described from Papua New Guinea and compared with G. acanthochirus, G. armatus and G. laurae, three similar species of the genus from the Caribbean and Indo-West Pacific. Glypturus motupore is found intertidally and subtidally to depths of 30 m. The species processes large quantities of sediment and subtidally builds volcano-shaped mounds up to 46 cm high. Burrows are complex, extending up to 1.5 m deep and 2 m laterally. Burrows are lined with fine-grained sediments and include subsurface chambers accumulating coarse sediment.